Instruments for minimally invasive medical procedures can be directly manipulated manually or can be operated with computer control or computer assistance. However, computer manipulation of a medical instrument often places strict mechanical requirements on the medical instrument. In particular, the mechanical systems of a robotic medical instrument may need to have a tightly controlled response to actuator operation, so that a computerized control system can calculate actuator movement that will achieve a precise movement of the instrument. Actuator controlled medical instruments may also need docking structures that engage electronically controlled actuators. For these reasons and others, medical instruments that are suitable for computer assisted operation tend to be cumbersome or difficult to use manually.
FIG. 1 schematically illustrates a medical instrument that may be used in a robotic system for a minimally invasive medical procedure. (As used herein, the terms “robot” or “robotically” and the like include teleoperation or telerobotic aspects.) Instrument 100 includes a tool or end effector 110 at a distal end of a shaft 120. End effector 110 includes jaws 112 and 114 that are rotatably mounted. Jaw 112 is connected to a first pair of tendons 121 and 122, and jaw 114 is connected to a second pair of tendons 123 and 124. Additional tendons (not shown) may be connected in instrument 100 to a wrist mechanism or joints (not shown) that provide additional degrees of freedom for positioning and orienting end effector 110.
Tendons 121, 122, 123, and 124 apply forces and torques to jaws 112 and 114 when pulled by a backend mechanism 130 attached to the proximal end of shaft 120. Backend mechanism 130 may act as a transmission that converts the rotation of drive motors (not shown) into movement of tendons 121, 122, 123, and 124 and end effector 110. As shown, backend mechanism 130 includes one capstan 131, 132, 133, or 134 per tendon 121, 122, 123, or 124, and the proximal ends of tendons 121, 122, 123, and 124 respectively wrap around capstans 131, 132, 133, and 134 and then attach to preload systems 135, 136, 137, and 138. Preload systems 135, 136, 137, and 138 can be biased, e.g., include stretched springs, so that non-zero forces are applied to the proximal ends of respective tendons 121, 122, 123, and 124 through the full range of motion of end effector 110. With this configuration, when capstans 131, 132, 133, and 134 are free to rotate, the corresponding preload system 135, 136, 137, or 138 provides tension and avoids slack in tendon 121, 122, 123, and 124.
End effector 110 can be operated using drive motors that are under the active control of software executed in a controlled system that interprets human input (e.g., through master control input in a master-slave servo control system). In particular, four drive motors, which are provided in a docking port of a control system (not shown), can be respectively coupled to rotate capstans 131, 132, 133, and 134. Backend mechanism 130 may dock with an interface of the control system including motors or other actuators. When backend mechanism 130 is removed from the dock, handheld operation of backend mechanism 130 may be difficult particularly because of the shape of backend mechanism 130 and the accessibility of capstans 131, 132, 133, and 134 and because control of each degree of freedom of end effector 110 involves using two capstans, e.g., capstans 131 and 132 or 133 and 134.